Arcade emus and having a 2nd player

I know all the emus have the ability to make a second player. However, I can't find a way for both the 1st and 2nd player to play at the same time. Now, some games are a real stretch to play well on one PSP (like most of the fighting games), but some of the easier ones like the SCHMUPs and stuff like Super Puzzle Fighter would be extremely easy. Is there a way to enable this? Otherwise, I might have to dive into the PSP dev world (which I've been wanting to do for awhile, but never have).